It's because of a translation error.

For non-system applications, the signature of the newly installed version should be consistent with the signature of the installed version. If you cannot sign the exact same signature, you can only completely uninstall and reinstall (pay attention to backing up data).

The private key is a cryptographic system. The private key system means that the encryption and decryption keys are the same or can be easily derived, so the encryption and decryption keys are kept confidential. In encryption and signature applications, both public and private keys can be used.